Electronics FAQ – Your Multilingual Guide to Electronics

Importance of a current-limiting resistor in an LED circuit LED is basically a forward-biased diode: Like a revered biased zener, it has a fairly constant voltage drop of 1.5V to 3V. If you supply more than this voltage, even slightly more, a large current will flow through it, as there is no mechanism to absorb the excess voltage (LED - supply). Result: LED damage from overcurrent. Mechanism of current limiting resistor:  A resistor in series absorbs the voltage difference and sets a safe current through it. A series resistor also has a secondary purpose of setting the light intensity of the LED. Especially in a battery powered gadgets, it is important to conserve battery.

How to find out the remaining life of lead acid battery?    Judging a battery's remaining life from its terminal open circuit voltage wont give you a clear picture. Have you heard the story of ‘ Blind Men and the Elephant’? You need to know the battery's ‘ internal resistance’ . As the battery becomes old, its internal resistance increases. If it crosses the maximum allowable value, the battery is due for replacement. Find the maximum allowable internal resistance for your battery type from its manufacturer. A telltale sign of a weak battery is that it heats up under high load. Battery internal resistance:  Battery internal resistance:   It is formed due to the chemical composition of the battery. It is very easy to calculate internal resistance by applying a predetermined known (resistive) load on the battery. Measure load current and load voltage to calculate the internal resistance of the battery by applying simple Ohm’s law. Circuit to find out the internal resis...

  How a VFD Converts AC to DC | VFD Working Principle Explained | AC to DC Conversion in Variable Frequency Drives | Power Electronics Basics Need for AC to DC conversion in VFD:  By doing this, the VFD drive kills two birds with one stone, i.e. frequency control and voltage control. Induction motor speed control requires two major things… Frequency control Voltage control AC is converted to DC. This can be done by a single-phase or a three-phase AC input supply. E.g. arrangement of a single-phase inverter. Frequency control :  DC is inverted to variable frequency three-phase AC. To reduce harmonics,  the  PWM   technique is used to generate a sinusoidal current through the induction motor. Voltage control :  Alone, changing frequency to control the speed of the induction motor is not enough because when the speed changes, back emf also changes. At low speed, back emf is reduced, and the motor draws more current, which heats up the motor.   Voltag...

  Why a Capacitor Is Called a Non-Dissipative Element – Capacitor Energy Storage, Lossless Element, Ideal Capacitor Explained A capacitor is called a   non-dissipative element   because it   stores electrical energy in its electric field without converting it into heat   during ideal operation. Unlike resistors, which   dissipate energy as heat , capacitors   absorb energy and return it to the circuit . In real life, small losses exist due to dielectric leakage and ESR, but ideally, a capacitor is considered   lossless . Dissipation means the generation of heat: In the above circuit, power is dissipated across R1 and R2. A capacitor does not generate heat:  In the same manner, we may think that power is dissipated across C and R, but in reality, power is dissipated across R only. Why? Because a capacitor simply charges and discharges through R. In short capacitor is just absorbing and releasing charge. No current flows through the capacitor b...

  Why the Voltmeter is Connected in Parallel and the Ammeter in Series | Explained with Illustrations Measurement principle: Ideally, a measuring instrument must not alter the reading being measured. Loading effect of measuring instruments:  What does it mean? E.g. a voltmeter must not load the (voltage) source to alter the actual reading. The above circuit shows how a reading by the voltmeter is altered due to the loading effect as the input impedance of the voltmeter comes in parallel to the load. Open circuit voltage measurement:  Another example is measuring the open-circuit voltage with a voltmeter. The internal resistance of the battery or voltage source and the input impedance of the voltmeter form a voltage divider. That will decrease the actual voltage being measured. Why a voltmeter must have a high input impedance:  The input impedance of the voltmeter becomes critical for the voltage sources that have high internal impedance. For example, various process ...

  Are BLDC Motors AC or DC | Brushless DC Motor Working, Difference Between Brushed and Brushless DC Motor, Advantages and Applications Are BLDC motors AC or DC? Learn about brushless DC motor working, differences, advantages, and uses of BLDC, AC, and DC motors. Are BLDC motors AC or DC? A BLDC motor runs on DC voltage. We also find BLDC motors in Ceiling fans and washing machines that run on AC, but in that case, AC is first converted to DC by an SMPS or switch-mode Power Supply.  Why BLDC Motor run exclusively on DC?  The BLDC motor brain is called an 'Electronic commutator', which is nothing but an electronic switching circuit that only runs on DC voltage .  Nowadays, we find BLDC motors in Electric Vehicles that run on a DC battery pack.  Difference between Brushed v/s Brushless DC Motor:  A BLDC motor is very similar to the DC motor, but there are some basic differences in the construction. Let's understand that.  Conventional brushed DC motor: I...

Digital Volume Control in Modern Audio Amplifiers. What is the principle of a Digital Potentiometer and its role in audio amplifiers?  We all know antic audio amplifiers use analogue potentiometers. They become noisy due to dust and require frequent cleaning. Modern amplifiers use digital volume control, though the volume control knob looks the same, the circuit for the same is entirely different. It uses fixed resistors in a voltage divider configuration and switches them electronically to control volume. This is done in digital volume control. Digital volume control module:  Modern audio amplifiers no longer use an analogue potentiometer to control volume. How does volume control work in Audio Amps? The volume control knob of an audio amplifier is essentially a voltage divider. Voltage Divider principle:  The output of the pre-amp is scaled and given to the power amp. And this scaling is done by analogue potentiometer by turning the volume control knob of the amp. Digit...

  How to Wire 2-Way Switches to Control One Light Fixture | 2-Way Switch Wiring Diagram, Steps, and Connection Guide What is a two-way switch? You need ‘ Two Way ’ and not ‘three way’ as wrongly mentioned in the earlier answer. The technical name of the switch is   SPDT,   i.e. ‘ S ingle   P ole   D ouble   T hrow ’ switch. Uses of a Two-Way switch:  Staircase light control:  A two-way switch is used for the staircase light control from the two different locations.  Wiring diagram of Two-Way switches:  The most popular application of this switch is ‘Staircase light control’ and ‘Bed switch’. Wiring and function are shown in the following animation. Animation of the working of a Two-Way switch: Wiring diagram of Two-Way Switches:  FAQ Set: Q1. What is a two-way switch wiring system? A two-way switch system allows a single light fixture to be controlled from two different locations using two switches. Q2. Where is a two-switch light c...

  How RC Low-Pass and High-Pass Filters Work — Simple Explanation with Examples Let me provide you with a basic understanding that will clear up any misunderstandings you may have regarding the capacitor in a high/low-pass filter. Mechanism of High/Low Pass Filter: ‘Filter’ word is a bit misleading. It doesn’t take ON/FF-type action. Filter only reduces (voltage) gain for a certain frequency compared to the whole spectrum of the frequencies of interest. A filter is basically a Voltage Divider:  The filter works on a voltage divider principle. Let me clarify. So, the output voltage reduces proportionally to the value of resistors R1 & R2. In simple words, the larger the R1 and the smaller the R2, Vout will reduce compared to Vin. Can I use the above circuit as a low-pass filter? No, because resistance doesn't change its value proportionally to the frequencies . So our goal of reducing gain for a certain band of frequencies wont be fulfilled. We need to replace R1 or R2 with...